The present invention relates to a camera for slow synchro-flash photography.
Automatic cameras have been prevalent recently. Most cameras are equipped with an automatic focus means. Generally speaking, the middle part of the picture area is in focus in the case of an automatic focus camera. When a photographer tries to focus the camera on an object which is not in the center of the picture area, he must conduct the prefocus operation of setting the image of an object in the center of the picture area and measuring the distance from the camera to the main object before taking a photograph. Namely, in the case of a two-step type release button, when the button is pressed once, the distance from the camera to the object is detected and memorized in the camera. This operation is called "focus lock". After that, if a photograph is taken with the camera, changing the direction of it, the photograph can be taken in the state of focus lock with a correct camera-to-subject distance. This method of photography is called "pre-focus photography".
The case of conducting pre-focus photography using strobe light, is considered here. When a photograph is taken using a strobe light, the method usually used is that in which the diaphragm of a camera is automatically set according to the guide number of strobe light and the camera-to-subject distance. This method is defined as "flashmatic" in this specification. Accordingly, the part of the photograph which is in focus, is correctly exposed, but all the rest is not necessarily exposed correctly. In most cases, it is under-exposed. For instance, FIG. 13 shows a photograph of a person B with a night view A of low-brightness in the background. F in the drawing is the focus frame of the AF camera to adjust the focus automatically. In the case focus is adjusted on person B as shown in FIG. 13(a), the photograph is a portrait of the person, so exposure is adjusted according to the person and under-exposure of the night view causes no problem. But, when both the night view A and the person B are wanted to be photographed as shown in FIG. 13(b), the distance from the camera to the night view A is different from that to the person B. Therefore, a photograph is taken with the pre-focus method adjusting the focus on the person B. The result is the person B who is focus-locked, can be photographed with correct exposure. But the photograph of the night view A is under-exposed and only a dark photograph is taken.
In order to solve the problem, a photographing mode called "slow synchro-flash" is conventionally known. This method will be explained as follows. According to the method, main photographic objects in the picture area can be exposed correctly by strobe light and all the rest is exposed automatically according to photometric value measured by photometry means or exposed according to the optional exposure time. In this way, both photographic objects are correctly exposed.
But when the above-mentioned slow synchro-flash photography is conducted, the mode must be set by operating a switch. Switch operation in a dark place where strobe light is used, is difficult since the switch can not be seen well. Furthermore, beginners are not familiar with slow synchro-flash photography, so sometimes they do not know about slow synchro-flash photography at all, or even if they know, they tend to forget to set the slow synchro-flash photograph mode when taking a photograph because they are too preoccupied by a photographic object or timing to press the shutter.
The object of the present invention is to solve the problems mentioned above. First of all, the invention aims at providing a camera which can completely automatically determine whether strobe light is emitted or not according to the measured distance information and photometry information, and when strobe light is emitted whether the conventional strobe light photographing conditions with flashmatic exposure are adopted or not, and slow synchro-flash photographing conditions with exposure by natural light in addition to flashmatic exposure are adopted or not. Secondly, the invention aims at providing a camera which can take a photograph of not only the main object but also all the rest, with correct exposure, when taking a photograph with the pre-focus method using strobe light.